STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Dec. 31, 2022	Mar. 31, 2022	Mar. 31, 2021
Interest and Dividend Income, Operating [Abstract]
Interest income (excluding Payment-in-kind ("PIK") interest income)	$ 169,457
Dividend income	779
PIK interest income	2,662	$ 4,075	$ 6,506
Other income	2,711
Total Investment Income	175,609	213,155	216,749
Expenses
Management fees	26,621	36,142	36,434
Performance-based incentive fees	5,691	11,681
Interest and other debt expenses	59,363	55,020	55,416
Administrative services expense	4,188	5,835	4,765
Other general and administrative expenses	6,551	9,106	10,495
Total expenses	102,414	117,784	107,110
Performance-based incentive fee offset	(178)	(247)	(25)
Expense reimbursements	(770)	(343)	(362)
Net Expenses	101,466	117,194	106,723
Net Investment Income	74,143	95,961	110,026
Net realized gains (losses):
Net realized gains (losses) on Investments	(69,239)	(67,367)	(21,506)
Foreign currency transactions	273	(5,586)	(4,108)
Net realized gains (losses)	(69,239)	(67,367)	(21,506)
Net change in unrealized gains (losses):
Net unrealized gains (losses) on investments	18,036	53,771	23,341
Foreign currency translations	4,431	9,178	(13,591)
Net change in unrealized gains (losses)	18,036	53,770	23,341
Net Realized and Change in Unrealized Gains (Losses)	(51,203)	(13,597)	1,835
Net Increase (Decrease) in Net Assets Resulting from Operations	$ 22,940	$ 82,364	$ 111,861
Earnings (Loss) Per Share — Basic	$ 0.36	$ 1.28	$ 1.71
Non-controlled/Non-affiliated Investments
Interest and Dividend Income, Operating [Abstract]
Interest income (excluding Payment-in-kind ("PIK") interest income)	$ 143,564	$ 164,878	$ 178,277
Dividend income	61	560	753
PIK interest income	1,156	2,652	5,447
Other income	2,234	5,060	2,472
Net realized gains (losses):
Net realized gains (losses) on Investments	1,977	2,977	(13,113)
Net change in unrealized gains (losses):
Net unrealized gains (losses) on investments	(35,113)	2,184	69,431
Non-controlled/Affiliated Investments
Interest and Dividend Income, Operating [Abstract]
Interest income (excluding Payment-in-kind ("PIK") interest income)	363	190	118
Dividend income	718	1,290	1,308
PIK interest income	58	71	15
Net realized gains (losses):
Net realized gains (losses) on Investments	(2,224)	541	(4,285)
Net change in unrealized gains (losses):
Net unrealized gains (losses) on investments	(5,008)	15,398	3,894
Controlled Investments
Interest and Dividend Income, Operating [Abstract]
Interest income (excluding Payment-in-kind ("PIK") interest income)	25,530	35,043	25,624
Dividend income		2,059	1,691
PIK interest income	1,448	1,352	1,044
Other income	477
Net realized gains (losses):
Net realized gains (losses) on Investments	(69,265)	(65,299)
Net change in unrealized gains (losses):
Net unrealized gains (losses) on investments	$ 53,726	$ 27,010	$ (36,393)